Defense Data Network

At that time, the Automatic Digital Network (AUTODIN), carried most of the Defense Department's message traffic.

Starting in 1972, attempts had been made to introduce some packet switching into its planned replacement, AUTODIN II.

[4] Under its initial architecture, as developed by the Institute for Defense Analysis, the DDN would consist of two separate instances: the unclassified MILNET, which would be split off the ARPANET; and a classified network, also based on ARPANET technology, which would provide services for WIN, DODIIS, and SACDIN.

Both networks carried unclassified information, and were connected at a small number of points which would allow total separation in the event of an emergency.

DDN-NIC or Network Information Center (NIC) was located at the DDN Installation and Integration Support (DIIS) program office in Chantilly, Virginia.